fiebigc 
I would like to monitor the voltage of a LiPo battery pack that powers my AVR. Can I simply connect the 3.7v positive terminal of the battery to an ADC channel on my ATmega16? Or is it more complicated?
I've attached a simple schematic of the circuit that I've described.
Thanks in advance.
bobgardner I'd say you need to use a 3.3V regulator, and monitor the 3.7V thru a voltage divider, like a couple of 10K resistors.
fiebigc Yeah you're right I should be using a boost regulator. I've always used a 9V battery and a LM7805 in the past that I was mistaken when I made this drawing.
Is the basic concept of connecting the power terminal of the battery to the ADC sound?
krazatchu 
Ya, that will work...
You could connect Aref to 5v or if you want full scale, use a resistive divider from the 5v volt line to set Aref to 3.7v...
You could connect Aref to 5v or if you want full scale
If Aref = 5V, 4.9V, 4.8V, 4.7V, 4.6V, 4.5V, 4.4V,...
and the V+ is fed into the ADC input then one will always read that the V+ = Full Scale.
If the Vref is set to a reference that is truely independant of V+, i.e. a true reference voltage, then one can compare the slowly decreasing V+ against that FIXED reference. In practice, one might monitor V+/2, (through a resistive divider), and use a fixed reference, either internal, or external, (depending on the uC used...).
JC
fiebigc Thanks for the replies. I feel confident to move forward with my design.
If Vcc down to 2.7 volts is acceptable you could run the L version directly off the battery. Then get the battery voltage by measuring the internal 1.22v bandgap voltage using Vcc as a reference. That saves an io pin too.
